300 blackout mold

[sirgknight]

My son just purchased a Lee TL309-230-5R mold for his 300 blackout. I'm not familiar at all with the blackout. I would like to help him get the best functionality out of his mold. I have .309 and .311 sizing dies and also have a .30 checkmaker. Any suggestions would be appreciated.

[KYShooter73]

.30 checks and sized .311 works for me, ymmv. I seat mine as long as I can get, and still be able to manually eject a loaded round. In other words, ogive almost touching the lands. Also, watch the primer pockets, that is the weak point in the 300 blackout.

[sirgknight]

We are using WW lead. Shouldn't we water drop the bullets?

[KYShooter73]

Take what I say with a grain of salt my friend. I'm no expert, but the 300 blackout in supersonic is challenging. (I have no experience with subsonic.). I've had two Ar barrels, 16" carbine CMMG, and 14.5 inch MAS (with a Troy comp to make 16"). In the BO, I've used two powders, Lil'Gun and W296 (H110). Using the Lee .312-155 2r. Powder coated and LLA coated shoot the same using an Al gas check. I took both powders up .1gn at a time from min to max. 15.7gn of W296 was my winner. I then seated them to the crimp groove and worked my way longer. The longer I made it, the better accuracy I had. I ran out of powder as I was making the oal shorter to function properly in my AR. That is where I am stuck until I find more W296 or H110.

I always water drop as cast. If I powder coat, I water drop again after baking. I have played with tin and copper additives, but at the blackout's speed, Wd wheel weights work just fine for me.

[petroid]

Slug the bore and size .001-.002 over. Mine slugs a hair over .308. My lee push thru gives .310 which works fine. I powder coat and get no lead on bolt. I do water drop out kf the PC oven. I use h110 and reloader 7. Reloader 7 runs a bit dirty in subsonic. You need a 1:7 twist to stabilize this boolit at subsonic speeds.

[sirgknight]

I kinda felt that this would be a real challenge. When I started casting for my M1 Garand it was really fun to work up a good round for it and it took it took about 60 pulls of the trigger to get it where I wanted it. I would think that this project, since we're dealing with an AR, will be much more challenging. I don't know the twist on his barrel yet and we have not slugged it, but we will get all of the preliminaries completed and go from there. I do have a good supply of H110 powder and a chronograph. Some 1680 would also be nice to try if I can find some.